I kept the Crown trucks but cut off the rapidos, used MTL1015 as recommended by Bowser. Using flathead screws is essential for the couplers, otherwise the axle is rubbing on the screw head. The plastic wheels don't roll that well, I first tried FVM 3302 and ended up with FVM #3311 wide thread wheelsets. Since the trucks mount is rather rigid, I had occasional derailments with the fine wheels. The larger flanges and threads of the 3311 work without derailments. The metal wheels turn freely in the Crown trucks.
I also use coal loads by JWD in most of my Bowser hoppers. They look good and add some weight.